The present invention relates to a method and to an apparatus for measuring the volumetric rate of flow of a fluid or gas. More specifically, the present invention appertains to an improved method and to an improved system of static parameters and of coordinated components to more accurately measure and maintain a constant discharge rate of flow for material in either a gaseous or a liquid state.
In order to provide for a small home heating system, a large industrial flow system, or any given discharge apparatus with an ongoing supply of a desired amount of a fluid or gas, a flow system must be designed to surmount the following obstacles. The system must accurately and continuously provide precise discharge rates to a consumption point even though the physical characteristics of the material carried therein may change with changes in pressure. The design must also reduce the inherent mechanical error, by eliminating inefficient or superfluous operations. A system which is involved in dispensing often expensive materials over a prolonged period of time magnifies an error, albeit small, into an onerous economic burden. A concomitant problem is to design a flow system that will conserve remaining non-renewable resources. Moreover, the system should be flexible enough to be adapted to any use where it is necessary to transport and accurately dispense a flowing material. For example, the system should be able to supply not only traditional forms of petrochemical energy, but newer energy alternatives such as methanol and liquified petroleum gas as well.
Heretofore, there have been many attempts to provide flow systems to accurately and continuously supply diverse fluids and gases to a point of consumption. As a general rule, available hydraulic and gas flow systems rely on feedback mechanisms which are responsive to internal and external changes in pressure. Some systems rely on by-pass lines to monitor and respond to changes in conduit line pressures caused by changes in discharge line pressures. Other systems are dependent upon such mechanical devices as springs, pistons, and diaphragms, fashioned from a variety of flexible materials, which continually adjust the internal pressures in response to changes in discharge line or supply line pressures. Finally, there are still other systems which employ very sophisticated electronic components, such as sonic nozzles or computers, to compensate for pressure variance by increasing or decreasing the velocity or pressure of the substance flowing through the system.
Notwithstanding the design of the prior art system, the general operative principle at work within the system is related to the ability of the internal parts from which the pressure or flow regulating components of the system are assembled, to compensate for changes in supply line and discharge line pressure. The internal readjustments allow the pressure differential across the component to be kept constant. In purely mechanical prior art systems, the basic operative kinetics are dependent upon keeping the pressure differential, that is, the same proportional difference between the pressure maintained upstream from the pressure regulating device, constant, without regard to internal or discharge rates of flow. The constant pressure differential, which reflects the difference between the inlet and outlet pressures, is maintained by the constant internal readjustment of pressure regulating parts. Thus, the pressure within the system may vary widely, with the outlet pressure rising in response to the rise in the inlet pressure, for as long as the difference in the pressures remains the same, the prior art system will function as anticipated. Generally, a constant pressure differential between the inlet and outlet pressures is obtained by varying the orifice area through the pressure regulating component. This internal adjustment is effected by the internal upward and downward movement of such parts as springs, pistons or diaphragms which open or close the orifice in response to changes in pressure. As a result, the discharge rate of flow is left to be regulated by either an auxiliary system or the discharge apparatus itself.
Mechanical flow systems, as described in the prior art, suffer from an inherent design flaw which is related to the self-adjusting nature of the feedback or compensation mechanism. The constant internal adjustment procedure, to maintain a constant pressure differential, is translated into a dispensing error where either inadequate or excessive amounts of the flowing material are conveyed to the waiting boiler, mixing vat or other receiving apparatus. With only the pressure differential remaining constant, such parameters as conduit line pressures, velocity of the flowing material and the effective orifice area through the components are left to vary, making the discharge accuracies of prior art systems at a given time only as accurate as the ability of the device to respond to changes in exogenously generated pressures. The problem raised hereinabove is purely practical. Such exigent circumstances as the partial occlusion of an oil burner's nozzle which arises periodically due to the introduction of foreign matter into the system, causes an increase in discharge line pressure. In order to overcome this impediment, prior art systems must follow the sequential process outlined below. Firstly, the change in pressure must be perceived by the system. Secondly, the internal part of the affected component must change its position in response to the altered condition. Thirdly, and finally, the system must reach an equilibrium range where the internal workings within the pressure or flow regulating component come to rest at a new adjustment level. As a result of this adjustment process, the system is no longer able to supply the minimum amount of the material necessary for the discharge apparatus to function with the greatest efficiency.
The reason underlying this error is related to the system's need to maintain a constant pressure differential. A constant pressure differential, characterized by constantly changing inlet and outlet pressures, results in a constantly changing discharge pressure. By varying the discharge pressure the force which drives the material into the waiting discharge apparatus is by necessity changed. Thus, greater or lesser amounts of the material are forced through the fixed aperture of the discharge apparatus. Generally, a partially blocked discharge route causes an increase in pressure which leads to the dispensing of excessive or inadequate amounts of the material.
Electronic systems, on the other hand, respond to pressure changes which take place outside the system in the following ways. Some systems electrically activate the internal pressure regulating parts to change internal pressures to keep the pressure differential constant. Other systems increase the rate of flow of the material through the system in response to the changed conditions at the discharge point.
Another problem inherent in systems whose internal parts are in continual motion is material fatigue which prevents individual parts from accurately responding to changes in pressure or altered flow rates. After a finite period, springs, pistons and diaphragms lose their original resiliency and ability to respond to changed operating conditions. This problem is exacerbated where viscous or corrosive materials are to be dispensed.
Prior art systems, whether mechanical or electronic, are inherently expensive to produce due to the sophistication necessary for producing pressure responsive parts. The systems described in the prior art require frequent recalibration to avoid ongoing discharge errors, and the more sophisticated electronic systems respond only to the ministrations of highly skilled repair persons.
Therefore, the principal object of the present invention is to provide a linear flow system of static parameters to accurately and continuously maintain a constant rate of flow of a fluid or a gas to a discharge point despite significant fluctuations in supply line and discharge line pressures. An explanation of the static nature of the present invention follows. The system, composed of a downstream pressure regulating device, a flow regulating device and a back pressure regulating device, connects each device in a linear fashion by conduit. After the system is assembled, each metering and regulating component is adjusted to a set position. This position reflects a predetermined constant pressure and constant flow rate value. The present invention is designed so that constant pressures and flow rates may be maintained within the conduit so that once the constant values are attained the pressure or flow components will not vary the level. Therefore, once the system is adjusted, the internal workings of the pressure and flow regulating components remain unmoving or static.
The flowing material enters the system via a conduit system and a pumping apparatus provides the initial unregulated rate of flow and pressure. An initial constant pressure P1 is obtained by setting a downstream pressure regulating device to the desired conduit pressure level. A flow rate is then set by a metering device to provide a constant rate of flow through the system and to the discharge point. A second conduit line pressure P2 is obtained by an upstream or back pressure regulating device. The back pressure regulator maintains a constant upstream conduit line pressure in the conduit line downstream from the flow regulating device. Finally, a synergistic pressure buffering system, composed of one or more pressure regulating devices, is adapted to protect the constant conduit line pressures. From the above sketch, it is evident that there is no need for a by-pass line to sample internal conditions and to regulate the system; a linear self-maintaining system results.
A concomitant object of the present invention is to provide a system that will withstand dramatic fluctuations in supply line and discharge line pressures.
Still another object of the present invention is to provide a highly accurate system which is capable of easy assembly and which is constructed from the following readily obtainable components of ordinary design: a conduit or tubing system, one or more downstream pressure regulators, a flow metering device, and one or more upstream pressure regulators. The result is an extremely inexpensive yet precise system, the overall accuracy being limited only by the accuracy of the individual components.
A further object of the present invention is to provide a flow system which has virtually no moving parts and few significant maintenance needs. The system at hand may be easily serviced by replacing the inexpensive components, if readjustment is not economically feasible.
Yet another object of the invention is to provide an integral sensing system to monitor and respond to radical changes in conduit line pressure and flow. It is contemplated that a servo-mechanism be adapted to sound an alarm so that readjustment or replacement of a part may be effected, or to deactivate the system and stop the flow of the material completely.
Another object is to provide a linear system which does not rely on a by-pass line to monitor and sample internal pressures and flow conditions.
Another object of the invention is to provide a flow system that will transport a great variety of substances including viscous and corrosive materials.
A further object of the invention is to provide a system that allows the chosen fluid or gas to be dispensed within a prescribed range of pressures.
In accordance with the objects stated hereinabove, the present invention offers a system of static parameters for dispensing precise amounts of fluids or gases at a constant rate of flow. The material, like heating oil, is pumped into the system from a storage facility at a point remote from the system, and enters the system at a base rate of flow and a base pressure Po. One or more pressure regulators modify the downstream pressure of the incoming material, thus protecting the static parameters of the system from significant fluctuations in inlet or supply line pressure. Located downstream from the buffering series of pressure regulators, a pressure regulator of ordinary design modifies the unregulated pressure Po giving rise to a constant conduit line pressure P1. The material flows on through the essentially linear conduit system to a flow regulating device, such as a metering valve, where by dilating or constricting the orifice through the component, a constant rate of flow may be preserved within and without the system. An upstream pressure regulating device or back pressure valve reduces the pressure of the flowing material to a constant value expressed as P2 in the conduit located upstream therefrom. One or more upstream regulating devices buffer and protect the P2 pressure, as the series of pressure regulating devices buffer and protect the P1 pressure, from changes in discharge line pressure. The number of buffering components to be interposed is based on the expectation of pressure changes; the likelihood of significant change increases with the size of the system and with the number of related discharge branches. The material exits at a constant rate of flow and a reduced pressure P3, allowing a discharge apparatus to dispense the material at a constant rate and within a range of pressures P4. A pressure gradient is formed through the system wherein the inlet pressure is not only greater than the outlet pressure, but also is greater than the intervening pressures.
Although most pumping facilities incorporate various kinds of emergency switches or by-pass lines, the present invention is designed to utilize such sensing devices as flow switches to relay unexpected and potentially damaging changes in flow rates and pressures to the servo-mechanism. The servo-mechanism can then shut down the system. This fail-safe feature protects both the individual components and the boiler, mixing vat, or other receiving apparatus which is supplied by the system. In addition, a pair of pressure switches may be integrally connected within the discharge line to allow the system to provide a range of discharge pressures without adversely affecting the upstream conduit pressures which must remain constant.
Other objects, advantages and features of the flow system of static parameters, which is the subject of the present invention, will become apparent when the drawings are taken with reference to the description and to the appended claims.